The pursuit of a sustainable energy future is a mankind long dream. For most of the twenty-first century, energy sustainability has become a pressing matter. Politicians, scientists and engineers have looked for energy resources that meet two main sustainable energy criteria: the harvest, as well as the release, of reaction products causes little or no damage to the environment, and nature can replenish itself between two harvesting periods. The energy resources that account for most of the energy used today, such as fossil fuels, do not pass the sustainable energy criteria. They are quickly being depleted from use, while increasing the environmental pollution.
Hence, sustainable energy resources that will not diminish over time, and whose availability will not depend on price or market fluctuations, are being investigated. In the last decade, the use of such renewable resources has increased. As an example, from 2000 to 2007, the photovoltaic (PV) power production increased from 1000 MW to almost 8000 MW in countries belonging to the International Energy Agency—Photovoltaic Power System (IEA-PVPS). The use of sustainable energy resources is changing the way the electric grid network is operated and designed.